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-{{a|design|}}{{d|Stochastic|/stəˈkæstɪk/|adj|}}
+{{a|systems|}}{{d|Stochastic|/stəˈkæstɪk/|adj|}}
-Of an event, to have a random distribution or pattern to which one may assign a [[probability]] but may not predict precisely. To be compared with [[deterministic]] (where one can predict the event precisely) and [[uncertain]] where one cannot even assign a probability.
+Of an independent event, to be random: to have a calculable [[probability]] of occurring that is less than one and greater than zero. To be predictable by reference to probability only.
-The outcome of rolling dice is stochastic: there are 36 possible outcomes, each of them is equally likely (1/36), but it is impossible to determine which will happen next time you roll the dice. Nonetheless, you know the probability of a given outcome is 0.02777 recurring.
+To qualify as a random distribution, events must be independent, each value must have a non-negative value, and the value of all events must add to 1. There must be a finite possible number of events.
-The price of a stock market index at a point in the future is ''sort of'' stochastic, in that it must be a number and that number must  be between zero and the total value of all issued currency in the world, but beyond that it is not possible to accurately assign a [[probability]], as [[Standard deviation|David “25-Sigma-Several Days-In-A-Row” Viniar]] would — probably? — tell you. So it isn’t really stochastic. To qualify as a random distribution, events must be independent, each value must have a non-negative value, and the value of all events must add to 1. There must be a finite possible number of events.
+Compare with [[deterministic]] (describing an event that is precisely predictable, such that it has a probability of 1) and [[uncertain]] (describing an event which is not independent or where controlling conditions are incomplete or unknown such that you cannot assign a probability at all.
+===Examples===
+Tossing a coin or rolling dice is stochastic: there are discrete outcomes, each of them is equally likely, but it is impossible to know which will come up in a given instance. Nonetheless, you know the probability of a given outcome exactly.
+The next word uttered by a conscious human is neither deterministic not stochastic. It is not governed by, or explainable in terms of, probabilities.
+The price of a stock market index at a point in the future ''seems'' stochastic, in that it must be a number and that number must  be between zero and the total value of all issued currency in the world, but it isn’t. You can’t assign [[probabilities]] to dependent events controlled by human agency, as [[Standard deviation|David “25-Sigma-Several Days-In-A-Row” Viniar]] would — probably? — tell you. So it really isn’t stochastic.
 What Elon Musk is going to say on [[Twitter]] tomorrow is ''uncertain''. There is no way of predicting it, or even assigning a probability to it. It is ''not even random''.